Porous adhesive sheet, semiconductor wafer with porous adhesive sheet and method of manufacture thereof

ABSTRACT

A porous adhesive sheet  1  having plural through holes  2  running in about parallel with each other in the thickness direction A of an adhesive organic film  3 , wherein the through holes have about congruent sections in the diameter direction from one opening  2   a  to the other opening  2   b  and a production method thereof, and a semiconductor wafer with a porous adhesive sheet  31 , which includes a semiconductor wafer  32  having an electrode  33 , the porous adhesive sheet  1  adhered to the semiconductor wafer, and a conductive part  34  formed by filling a through hole  2  located on the electrode  33  with a conductive material, and a production method thereof are provided.

This is a divisional of Entry of National Stage application Ser. No.10/181,020 filed Jul. 12, 2002 now U.S. Pat. No. 6,890,617; thedisclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a porous adhesive sheet, particularly aporous adhesive sheet that can be suitably used as an adhesive materialfor mounting a semiconductor, and a preferable production methodthereof. The present invention also relates to a semiconductor waferwith the above-mentioned porous adhesive sheet, and a preferableproduction method thereof.

BACKGROUND ART

As a method of semiconductor mounting capable of achieving higherproductivity, a bare chip mounting has been developed, wherein asemiconductor element having a bump and a substrate are joined and thespace between them is filled with an underfill material by immersion andthe like. In such bare chip mounting, an electrode on a semiconductorelement is formed into a convex shape (bump) using, for example, asoldering paste, and this bump is metal joined with a circuit on asubstrate and the gap between the semiconductor element and thesubstrate (other than the bump) is filled with an underfill material toform a bump junction.

A semiconductor element mounted by this method, however, easily suffersfrom the stress produced by the difference in the expansion coefficientsof the substrate and the semiconductor element, often resulting in adefective bump junction. In this event, a greater distance between thesemiconductor element and the substrate during the above-mentionedjunction reduces the stress produced by the difference in the expansioncoefficients of the substrate and the semiconductor element. However, agreater distance between the semiconductor element and the substraterequires a greater diameter of the bump to match the distance, thusmaking a fine-pitch connection difficult to achieve.

Because the underfill material comprises a liquid resin for adhesion,the fluidity of the adhesive material needs control. Thus, thedevelopment of an adhesive material capable of simple adhesion isdesired to replace the liquid resin.

As a different method for semiconductor mounting, a method is known,wherein a semiconductor element and a circuit board are adhered using ananisotropic conductive film to achieve conduction. When compared withthe above-mentioned method for forming a bump junction, however, theconnection resistance becomes higher. Therefore, when this method isused for a high speed semiconductor device, many problems occur, such asheat generation in a semiconductor element, noise signal duringoperation and the like.

To obviate these defects, the present inventors conceived an idea ofadhering, to a semiconductor wafer, a porous adhesive sheet generallyused for adhering a filter and the like to secure gas permeation,filling part of the through holes in the porous adhesive sheet with asoldering paste to electrically connect the semiconductor element andone side of the porous adhesive sheet, forming a bump on one side of theporous adhesive sheet to connect the circuit side of the substrate,thereby to improve connection reliability with the circuit side. As aporous adhesive sheet usable for such semiconductor mounting, one havingthrough holes of a regular shape, which are hardly closed in an adhesionstate, is preferable.

When a production method comprising forming a number of fine throughholes in a formed adhesive sheet to give a porous adhesive sheet isemployed, a resin, which is a sheet material, flows during adhesion andfills the through holes, failing the conduction.

When a production method of a porous adhesive sheet is employed, whichcomprises extending a formed organic film to give an adhesive sheet andforming a number of fine through holes, moreover, respective throughholes thus formed do not have a regular shape. When the organic filmitself has adhesiveness that allows adhesion by heating and/orpressurization, the opening of some of the through holes is easilyclosed up during adhesion, and the opening ratio of the porous adhesivesheet drastically decreases before and after the adhesion. With suchproduction method, formation of through holes such that the porousadhesive sheet has such opening ratio as to achieve the object isdifficult.

The present inventors assumed the following processes for forming anumber of fine through holes in an organic film. These methods providethrough holes having a regular shape, but each has the followingproblems.

(1) Drilling

Due to low productivity, unsuitable for the production of a porousadhesive sheet having a number of fine through holes.

(2) Punching

Incapable of forming fine through holes, unsuitable for production ofthe above-mentioned porous adhesive sheet.

(3) Laser Beam Machining

A porous adhesive sheet wherein each through hole has an about trapezoidshape is produced, due to which the opening ratio (area ratio of openingof through holes to the entire porous adhesive sheet) of one surface ofone side differs greatly from that of one surface of the other side uponformation of the through holes in this porous adhesive sheet, the ratioof the minimum area Smin to the maximum area Smax, Smin/Smax (%), of thesections in the diameter direction from one opening to the other openingof a through hole is 40%–80%, wherein the area permitting adhesion onthe side having a greater opening ratio becomes smaller than that on theside having a smaller opening ratio. This has a consequence that theside having a greater opening ratio of the adhesive sheet fails to haveadhesiveness permitting its adhesion to an adhesion target.

(4) Photoprocessing

As in the case of laser beam machining, each through hole has an abouttrapezoid shape. In this porous adhesive sheet, the ratio of the minimumarea Smin to the maximum area Smax, Smin/Smax (%), of the sections inthe diameter direction from one opening to the other opening of athrough hole is 40%–80%. As a result, a porous adhesive sheet whereinthe opening ratio differs greatly between one surface of one side andone surface of the other side is unpreferably produced.

The present invention aims at solving the above-mentioned problems andprovides the following.

-   (1) A porous adhesive sheet suitably used also in the field of    electronic materials.-   (2) A suitable production method of the adhesive sheet of the    above-mentioned (1) (e.g., a porous adhesive sheet having through    holes having a regular shape and difficult to close in an adhesion    state.-   (3) A semiconductor wafer with a porous adhesive sheet, which is    suitable for bare chip mounting, and a suitable production method    thereof.

DISCLOSURE OF THE INVENTION

The present inventors have conducted intensive studies in an attempt tosolve the above-mentioned problems and found that a porous adhesivesheet free of the above-mentioned problems can be obtained by employinga specific structure and/or a specific production method, that thisporous adhesive sheet is highly preferable as an adhesive material forbare chip mounting, and that production of a semiconductor wafer with aporous adhesive sheet can further improve its productivity, whichresulted in the completion of the present invention.

Accordingly, the present invention provides the following.

-   [1] An adhesive sheet having plural through holes running in about    parallel with each other in the thickness direction of an organic    film, wherein each through hole has an about congruent section in    the diameter direction from one opening thereof to the other opening    thereof.-   [2] The porous adhesive sheet of the above-mentioned [1], wherein    the through hole maintains its opening even after adhesion.-   [3] The porous adhesive sheet of the above-mentioned [1], further    comprising an organic material layer having a softening temperature    higher by 10° C. or more than the softening temperature of the    organic film, which layer surrounding the aforementioned through    holes.-   [4] The porous adhesive sheet of the above-mentioned [1] or [3],    which comprises, on at least one side of the organic film, an    adhesive material layer having the entirety or a part of the through    holes present in the organic film and plural communication holes    communicating in the aforementioned thickness direction, wherein the    adhesive material layer is composed of a thermoplastic resin or    thermosetting polymer having a softening temperature lower than that    of the organic film by 10° C.–30° C., and has such thickness as not    to close up the through holes in the organic film in an adhesion    state.-   [5] The porous adhesive sheet of the above-mentioned [1] or [3],    which comprises, on at least one side of the organic film, an    adhesive material layer having the entirety or a part of the through    holes present in the organic film and plural communication holes    communicating in the aforementioned thickness direction, wherein the    adhesive material layer is composed of a thermosetting oligomer    having a melt start temperature lower than the softening temperature    of the organic film by not less than 10° C., and has such thickness    as not to close up the through holes in the organic film in an    adhesion state.-   [6] The porous adhesive sheet of any of the above-mentioned [1] to    [5], wherein, when at least a part of the through holes is filled    with a conductive material, respective conductive materials are    insulated from each other.-   [7] A production method of a porous adhesive sheet, which comprises    a step for forming a wire-containing film for forming an adhesive    organic film having plural wires running in about parallel with each    other in the thickness direction thereof, and a wire-removing step    for removing the wire in said organic film.-   [8] The production method of the above-mentioned [7], wherein the    wire is covered with an organic material having a softening    temperature higher than that of the organic film by not less than    10° C.-   [9] The production method of the above-mentioned [7] or [8], further    comprising, between the aforementioned step for forming a    wire-containing film and the wire-removing step, a wire protrusion    step for protruding a wire end on at least one surface side of the    wire-containing film from the film surface, and an adhesive material    layer-forming step for forming an adhesive material layer composed    of a thermoplastic resin or thermosetting polymer having a softening    temperature lower than that of the organic film by 10° C.–30° C.,    which fills a difference between the aforementioned wire protrusion    and the film surface.-   [10] The production method of the above-mentioned [7] or [8],    further comprising, between the aforementioned step for forming a    wire-containing film and the wire-removing step, a wire protrusion    step for protruding a wire end on at least one surface side of the    wire-containing film from the film surface, and a step for forming    an adhesive material layer composed of a thermosetting oligomer    having a melt start temperature lower than the softening temperature    of the organic film by not less than 10° C., which fills a    difference between the aforementioned wire protrusion and the film    surface.-   [11] The production method of any of the above-mentioned [7] to    [10], wherein the wires are insulated from each other.-   [12] A semiconductor wafer with a porous adhesive sheet, which    comprises a semiconductor wafer having at least one electrode on at    least one surface thereof, the porous adhesive sheet of the    above-mentioned [6], which is adhered to said surface of the    semiconductor wafer, and a conductive part formed by filling each    through hole located on the electrode of the semiconductor wafer of    the porous adhesive sheet with a conductive material.-   [13] A production method of a semiconductor wafer with a porous    adhesive sheet, which comprises an adhesion step for adhering the    porous adhesive sheet of the above-mentioned [6] onto at least one    surface of a semiconductor wafer having at least one electrode on at    least one surface thereof, and a conductive part-forming step for    filling a through hole located on the electrode of the semiconductor    wafer of the porous adhesive sheet with a conductive material and    joining the electrode and the conductive material.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a simplified sectional view of one preferable embodiment ofa porous adhesive sheet 1 of the present invention.

FIG. 2 shows a simplified sectional view of one preferable embodiment ofa porous adhesive sheet 11 of the present invention.

FIG. 3 shows a simplified sectional view of one preferable embodiment ofa porous adhesive sheet 21 of the present invention.

FIG. 4 shows a simplified sectional view of one preferable embodiment ofa semiconductor wafer with a porous adhesive sheet 31 of the presentinvention.

FIG. 5 shows a simplified sectional view of one preferable embodiment ofa semiconductor wafer with a porous adhesive sheet 41 of the presentinvention.

FIG. 6 shows a simplified sectional view of one preferable embodiment ofa semiconductor wafer with a porous adhesive sheet 51 of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described in detail in the following.

FIG. 1 shows a simplified sectional view of one preferable embodiment ofa porous adhesive sheet 1 of the present invention. FIG. 1 shows asectional view on one virtual plane in parallel with the thicknessdirection A of the porous adhesive sheet 1 and passing a through hole 2.The porous adhesive sheet 1 shown in FIG. 1 is an adhesive organic film3 having plural through holes 2. The through holes 2 run in aboutparallel with each other in the thickness direction A of the organicfilm 3, penetrate the organic film 3 generally along the thicknessdirection A thereof, and have openings 2 a and 2 b respectively on onesurface 1 a of one side A1 of porous adhesive sheet 1 in the thicknessdirection and on one surface 1 b of the other side A2 thereof in thethickness direction. In the present invention, the thickness directionof each of the porous adhesive sheet 1 and the organic film 3 is thesame direction A.

While the central axis B of the above-mentioned through hole 2 may belinear or curved, it is preferably linear. The through hole 2 has, fromits one opening 2 a to the other opening 2 b, about congruent sectionsin the diameter direction. In the present specification, by the “sectionin the diameter direction” is meant that in a virtual plane Cperpendicular to the central axis B of each through hole 2. By theabove-mentioned “about congruent” is meant a substantially the sameshape. In other words, it means that the shape and area of each sectionin the diameter direction are the same from one opening 2 a to the otheropening 2 b of through hole 2 in the present invention, including aproduction error. The above-mentioned production error means that, ofthe sections in the diameter direction from one opening to anotheropening of a through hole, the ratio Smin/Smax (%) of the minimum area(Smin) to the maximum area (Smax) is preferably 85%–100%, morepreferably 90%–100%. The through hole 2 in the present invention doesnot include one having a shape about congruent in the aforementionedsection in the diameter direction but not almost identically-shaped,namely, a twisted shape.

The shape of the section in the diameter direction of through hole 2 isnot particularly limited and is appropriately determined according tothe use of the porous adhesive sheet of the present invention. It may beround, square, triangular or other shape, preferably round, morepreferably circular. The sectional shape of each through hole 2 in avirtual plane C perpendicular to the central axis B may be aboutcongruent or different from each other. More preferably, through holes 2are realized to have an about congruent sectional shape. In FIG. 1,every through hole 2 has an about congruent circular sectional shape.

As mentioned above, plural through holes 2 are about parallel with eachother, and penetrate the aforementioned organic film 3 generally in thethickness direction A. The aforementioned through holes 2 do not need tobe parallel with the thickness direction A of organic film 3, as long asthey are about parallel with each other. Preferably, they are parallelwith the aforementioned thickness direction A and parallel with eachother. When the through holes 2 have the aforementioned sectional shapeof an about congruent circle, as shown in FIG. 1, they preferably have adiameter of 18 μm–150 μm, more preferably 30 μm–100 μm. When the throughholes 2 have the aforementioned sectional shape other than a circle,they preferably have a similar sectional area as that of theabove-mentioned circle.

The porous adhesive sheet 1 has the above-mentioned plural through holes2 to the extent that the adhesiveness of a practical level is ensured.To be specific, the number of through holes 2 is determined to make theratio of opening of the porous adhesive sheet 1 at ambient temperature(23° C.) preferably 30%–80%, more preferably 40%–70%. The ratio ofopening refers to the proportion of the total of the opening areas S2 ofthe through holes 2 to area S1 that includes each opening 2 a of thethrough hole 2 on one surface of one side of porous adhesive sheet 1,for example, one surface 1 a of one side A1 in the thickness direction.

Different from conventional porous adhesive sheets having through holesformed by laser beam machining or photoprocessing, the porous adhesivesheet 1 has similar ratio of opening of one surface 1 a of one side A1in the thickness direction and that of one surface 1 b of the other sideA2 in the thickness direction, and adhesiveness of a practicallyfunctional level.

The porous adhesive sheet of the present invention may have a structureof a single layer or a laminate. As shown in FIG. 1, when the adhesivesheet 1 includes an organic single layer film 3, the organic singlelayer film itself needs to have adhesiveness. When it is a laminate, asmentioned below, the outermost layer of at least one side needs to haveadhesiveness. In this case, the organic film itself may not haveadhesiveness. The porous adhesive sheet 1 has a thickness D1 ofpreferably 30 μm–500 μm, more preferably 50 μm–300 μm.

When the sheet has a single layer as mentioned above, organic film 3preferably has adhesiveness that permits adhesion at least by heating,more preferably by heating and pressurization. The material of organicfilm 3 having such adhesiveness is not particularly limited as long asit is a resin that develops adhesiveness at least by heating, and may bea known adhesive material such as thermoplastic resin, unreactedthermosetting resin composition and the like. As such material, athermoplastic resin film or thermosetting polymer film obtained byforming these resins, which has a softening temperature of preferably100° C.–250° C., more preferably 150° C.–200° C., is used. When amaterial having the above-mentioned softening temperature of lower than100° C. is used, the adhesive sheet shows degraded adhesion reliability.When a material having the above-mentioned softening temperature of over250° C. is used, the materials including those around an aluminumelectrode on a semiconductor element and the like may be deteriorated oradhesion operability may be degraded. The “softening temperature” in thepresent specification refers to an inflection point temperature asmeasured upon temperature increase at 10° C./min on a tension mode ofTMA (thermomechanical analysis). The organic film 3 to be used in thepresent invention particularly preferably becomes adhesive in atemperature range of 105° C.–220° C. by pressurization at 0.49 MPa–2.94MPa generally in the aforementioned thickness direction. In general, aporous adhesive sheet obtained by forming through holes in theabove-mentioned . organic film and adhered to an adhesion target at atemperature higher than the softening temperature of the organic film by5° C.–10° C. suppresses changes in shape of through holes and retainssuitable adhesiveness.

The material of the organic film 3, when it is a thermoplastic resin,includes, for example, polyamide resin (softening temperature: 160° C.),polyimide resin (softening temperature: 190° C.), saturated polyesterresin (softening temperature: 170° C.) and the like. Of thethermosetting polymers, polycarbodiimide resin is preferable. Theseresins are determined according to the object and may be used alone orin combination of two or more kinds thereof. The thermosetting resin tobe used for organic film 3 shows self-supporting property during filmforming and allows measurement of the softening temperature. As usedherein, by the “thermosetting polymer” is meant a solid one in what iscalled a B-stage, which is obtained by polymerization or condensation ofan unreacted thermosetting resin composition (monomer) to give acrosslinkable polymer.

The porous adhesive sheet 1 maintains the openings 2 a, 2 b of throughhole 2 even after adhesion of the adhesive sheet to an adhesion subject.Concretely, the openings 2 a, 2 b show a proportion of decrease from theabove-mentioned ratio of opening at an ambient temperature to that afteradhesion of preferably 0%–20%, more preferably 0%–10%. Because theporous adhesive sheet 1 shows regularity in the shape of through hole 2,and maintains openings 2 a, 2 b upon adhesion, the ratio of opening doesnot change drastically before and after adhesion, thereby retainingsufficient opening in the through holes.

The porous adhesive sheet of the present invention preferably has anorganic material layer surrounding the aforementioned through holes.FIG. 2 shows a simplified sectional view of one preferable embodiment ofa porous adhesive sheet 11 of the present invention, which is on onevirtual plane in parallel with the thickness direction A and passing athrough hole 12 and organic material layer 14.

The porous adhesive sheet 11 shown in FIG. 2 further has an organicmaterial layer 14 surrounding the through hole 12, in addition tothrough hole 12 and organic film 13 corresponding to the through hole 2and the organic film 3 of the porous adhesive sheet 1 shown in FIG. 1.

The organic material layer 14 shows self-supporting property and isproduced using an organic material having a softening temperature higherby at least 10° C., preferably at least 30° C., than the thermoplasticresin or thermosetting polymer that forms the organic film 13. As suchorganic material, one having a softening temperature of preferably notlower than 160° C., more preferably not lower than 170° C., ispreferable. Specific examples include polyamideimide resin (softeningtemperature: 170° C.), saturated polyester resin and the like. Anorganic material capable of satisfying the above-mentioned requirementsupon combination with materials forming the organic film 13 can be used.When an unreacted thermosetting resin composition is used as the organicmaterial forming the organic material layer 14, it is preferable thatthe composition become a thermoset resin having a three-dimensionalstructure when the organic material layer 14 has been formed.

As shown in FIG. 2, when the aforementioned sectional shape ofrespective through holes 12 is about a congruent circle, the organicmaterial layer 14 is preferably formed in a cylindrical shape having aconcentric circle with through hole 12. The thickness D2 then of theorganic material layer 14, or the linear distance between the outerperiphery and the inner periphery on a visual linear line extending inthe radial direction is preferably 1 μm–10 μm, more preferably 2 μm–8μm.

Such organic material layer 14 has a softening temperature higher thanthe softening temperature of the organic film 13. Therefore, when theabove-mentioned organic film 13 is softened by heating to permitadhesion, the organic material layer 14 does not transit to a softenedstate any more easily than the organic film 13 does. When compared witha case where such organic material layer is not formed, the shape of thethrough hole 12 can be easily retained. This has a consequence that theporous adhesive sheet 11 affords, besides the above-mentioned effects ofthe porous adhesive sheet 1 shown in FIG. 1, an effect that the openingof the through hole 12 is not easily closed up, and the decrease in theratio of opening before and after adhesion can be minimized. Inaddition, the through hole does not easily deform as a whole, therebyproviding a high grade porous adhesive sheet 11 permitting morefunctional use of the through hole.

The porous adhesive sheet of the present invention preferably has anadhesive material layer on at least one surface of the organic film. Theadhesive material layer has a communicating hole that communicates withthe entirety or a part of the through holes in the organic film in theabove-mentioned thickness direction. FIG. 3 shows a simplified sectionalview of one preferable embodiment of a porous adhesive sheet 21 of thepresent invention, which is on one virtual plane in parallel with thethickness direction A and passing a through hole 22 and an adhesivematerial layer 25 a.

The porous adhesive sheet 21 shown in FIG. 3 further has an adhesivematerial layer 25 a that forms a region excluding an organic materiallayer 24 on one surface 21 a of one side A1 in the thickness directionof the porous adhesive sheet 21, in addition to the through hole 71, anorganic film 23 and an organic material layer 24 corresponding to thethrough hole 12 and the organic film 13 and organic material layer 14 ofthe porous adhesive sheet 11 shown in FIG. 2. Thus, the porous adhesivesheet 21 of FIG. 3 is produced from a laminate of an organic film 23 andan adhesive material layer 25 a. The porous adhesive sheet 21 has athrough hole 22 consisting of a through hole 71 in the organic film 23and a communicating hole 72 that communicates with the through hole 71in the above-mentioned thickness direction A in this adhesive materiallayer 25 a. The communication hole 72 has about congruent sections inthe diameter direction with the through hole 71 and continuously rangeswith the same axis line. In other words, in the porous adhesive sheet 21of FIG. 3, as in the case of the aforementioned embodiments, the throughhole 22 is produced to have about congruent sections in the diameterdirection from its one opening to the other opening.

The adhesive material layer 25 a is produced from a thermoplastic resin,thermosetting polymer or thermosetting oligomer. When the adhesivematerial layer 25 a is produced from a thermoplastic resin orthermosetting polymer, one having a softening temperature lower thanthat of the organic film 23 by 10° C.–30° C. is used. When the adhesivematerial layer 25 a is produced from a thermosetting oligomer, onehaving a melt start temperature lower than the softening temperature ofthe organic film 23 by at least 10° C. is used. As regards thethermosetting resin in the present specification, the “unreactedthermosetting resin” refers to those in what is called the A-stage, the“thermosetting oligomer” refers to, from among those in what is calledthe B-stage, a semi-solid one that permits measurement of the melt starttemperature and does not permit measurement of the softeningtemperature, and the “thermosetting polymer” refers to, from among thosein what is called the B-stage, a solid one that permits measurement ofthe softening temperature. The “thermoset resin” in the presentspecification refers to a cured product in what is called the C-stage,where the thermosetting resin has been heat cured to have athree-dimensional structure. In the present specification, a merereference to a “thermosetting resin” includes the above-mentioned“unreacted thermosetting resin”, “thermosetting oligomer” and“thermosetting polymer”. In the present specification, the “melt starttemperature” refers to, when the above-mentioned adhesive material ismelted using DSC (differential scanning calorimeter), a temperature atthe point at which the tangent line toward said point intersects withthe base line, from among the respective points on the peak, obtained inresponse to the above-mentioned melting, on the differentialcalorimetric curve obtained by the melting.

When a thermosetting resin is applied, a liquid unreacted thermosettingresin composition containing a base resin and a curing agent isgenerally used. After applying this composition and the like, thereaction is carried out under an appropriate control by heating and thelike, whereby a thermosetting oligomer permitting measurement of a meltstart temperature can be obtained. The thermosetting oligomer has asoftening temperature of not higher than the ambient temperature, anddoes not permit determination of the softening temperature. In thepresent specification, therefore, the “melt start temperature” is setfor the thermosetting oligomer as mentioned above, which corresponds tothe “softening temperature” of a thermosetting polymer and athermoplastic resin.

The thermosetting polymer and the thermoplastic resin that afford asoftening temperature also permit determination of the melt starttemperature in the above-mentioned manner. A porous adhesive sheethaving an adhesive material layer produced from an adhesive materialhaving a softening temperature and a melt start temperature both lowerthan the softening temperature of the organic film by 10° C.–30° C. isalso encompassed in the present invention.

An adhesive material to produce such adhesive material layer when athermosetting polymer or thermoplastic resin is used has a softeningtemperature of preferably 120° C.–240° C., more preferably 150° C.–200°C., particularly preferably 160° C.–190° C. A thermosetting polymer orthermoplastic resin showing such a softening temperature is, forexample, a saturated polyester resin (softening temperature: 170° C.), apolyamide resin (softening temperature: 160° C.), a polycarbodiimideresin and the like. When a thermosetting oligomer is used, the meltstart temperature thereof is not higher than 170° C., more preferablynot higher than 150° C., particularly preferably not higher than 120° C.As a thermosetting oligomer having such a melt start temperature, thereis mentioned a semi-solid one obtained by heating an unreacted liquidepoxy resin composition or by other method. Such adhesive material isnot particularly limited as long as the above-mentioned requirements aremet, and those capable of satisfying the above-mentioned requirementsupon combination with materials forming the organic film 23 can be used.Particularly, a thermosetting oligomer of the above-mentioned epoxyresin is preferably used.

The adhesive material is generally liquid during formation of the layer,whether a thermoplastic resin, a thermosetting polymer or athermosetting oligomer is used. Therefore, when the adhesive materiallayer is too thick, the adhesive material bleeds out to possibly closeup the opening of the through hole 22. Thus, the adhesive material layer25 a should be formed such that the opening of the through hole 22 isnot closed, in consideration of adhesion conditions, viscosity andthickness. Particularly, when a thermosetting oligomer is used,viscosity easily decreases during thermal adhesion, and carefulprocessing is required including the determination of the adhesionconditions. As in the above-mentioned case where a porous adhesive sheetis realized with a laminate, at least the adhesive material layer, whichis the outermost layer, of the porous adhesive sheet should haveadhesiveness, and the organic film itself does not need to haveadhesiveness.

The adhesive material layer 25 a has a thickness D3 in theaforementioned thickness direction A, such that the through hole 22 isnot closed when the organic film 23 is adherable. Such thickness D3 ofthe adhesive material layer 25 a is, like the porous adhesive sheet 21shown in FIG. 3, for example, 1%–10%, preferably 5%–10%, of the diameterR1 of the through hole 22 when the aforementioned sectional shape of thethrough hole 22 is an about congruent circle.

Such adhesive material layer may not be formed on the entirety of atleast one surface of the organic film less the opening of each throughhole and the organic material layer. Preferably, as shown in FIG. 3, itis formed on at least one surface of the porous adhesive sheet 21 lessthe opening 71 a of each through hole 71 and the organic material layer24.

The porous adhesive sheet 21 having such adhesive material layer 25 acan provide the above-mentioned effects of the porous adhesive sheet 11of FIG. 2, and can improve the adhesiveness of the porous adhesive sheetsurface 21 a of the adhesive material layer 25 a. Forming such adhesivematerial layer here is considered to make each through hole easilyfilled after adhesion. However, because the adhesive material layer hasa given thickness to suppress such disadvantages, and because an organicmaterial layer is formed around the through hole, the through hole doesnot collapse easily, and the ratio of opening does not drasticallydecrease before and after adhesion. Therefore, a porous adhesive sheethaving improved adhesiveness and a higher grade can be provided ascompared to a structure free of an adhesive material layer.

Alternatively, the porous adhesive sheet of the present invention maynot have an organic material layer formed around the through hole but anadhesive material layer may be formed on at least one surface of theporous adhesive sheet except the opening of through holes.

The porous adhesive sheet of the present invention shows insulatingproperty wherein respective conductive materials are insulated from eachother, when at least a part of the through holes is filled with aconductive material. The porous adhesive sheets 1, 11 and 21 of theabove-mentioned FIG. 1–FIG. 3 all have the above-mentioned insulatingproperty. By the aforementioned state of being “insulated from eachother” is meant a state where respective conductive materials are notconducted with each other but insulated from each other within anorganic film. As the material to produce an organic film of the porousadhesive sheet having such insulating property, the aforementionedmaterials are suitable, and a linear distance between through holes ispreferably 1 μm–30 μm, particularly preferably 5 μm–20 μm. In the caseof the porous adhesive sheets 11 and 21, each of the organic materiallayers 14 and 24 is preferably produced from a material havinginsulating property. As the organic material to produce an organicmaterial layer having such insulating property, all the aforementionedmaterials are preferable.

In the porous adhesive sheet of the present invention further havingsuch insulating property, an electrode of a semiconductor element can beconducted by filling at least a part of the through holes with aconductive material, such as soldering paste and the like, and adheringthe sheet to a semiconductor element having an electrode. As such, theporous adhesive sheet of the present invention can be suitably used foradhesion accompanying electrical connection for wafer scale chip sizepackage, by adhering the sheet to a semiconductor wafer and dividing thesheet into small pieces to give semiconductor elements with a smallpiece porous adhesive sheet adherable to a substrate. Alternatively,when a high thermal conductive material, such as a silver paste and thelike, is used to fill a part of the through holes, the sheet can bebeneficially used as a high thermal dissipative adhesive sheet, and thesheet can be beneficially used as a low dielectric adhesive sheet whenthe through holes remain open. In the present specification, the porousadhesive sheet includes those having a through hole filled up, and asheet having all through holes filled up is also regarded a porousadhesive sheet.

FIG. 4 shows a simplified sectional view of one preferable embodiment ofa semiconductor wafer with a porous adhesive sheet 31 of the presentinvention, which is on one virtual plane in parallel with the thicknessdirection A and passing a through hole 2 and an electrode 33. Forsimplification, the size of the semiconductor wafer and that of theporous adhesive sheet are not on the same scale. A porous adhesive sheethaving the above-mentioned insulating property can be used beneficiallyas a material for bare chip mounting. The aforementioned bare chipmounting refers to a method of mounting a semiconductor, which comprisesplacing an adhesive material on a semiconductor wafer in advance,processing the laminate into small pieces and using the pieces formounting. A semiconductor wafer with a porous adhesive sheet of thepresent invention comprises a semiconductor wafer having one or moreelectrodes on at least one surface thereof, a porous adhesive sheet tobe adhered to one surface of the semiconductor wafer, and a conductivepart formed by filling a through hole in a porous adhesive sheet, whichis located on the electrode of the semiconductor wafer, with aconductive material. In FIG. 4, a semiconductor wafer with a porousadhesive sheet 31 is shown, wherein a porous adhesive sheet 1 shown inFIG. 1 is adhered to one side surface 32 a of the semiconductor wafer32, on which plural electrodes 33 are formed, and, of the plural throughholes 2 in the porous adhesive sheet 1, at least the through hole 2 thatcomes on the electrode 33 of semiconductor wafer 32 is filled with aconductive material to form a conductive part 34.

The conductive parts 34 of a semiconductor wafer with a porous adhesivesheet 31 are insulated from each other in an organic film 3 havinginsulating property. The conductive material to fill each through hole 2located on each of the above-mentioned electrodes 33 is not particularlylimited as long as it is a metal used for electronic material, but it ispreferably a soldering paste. Each conductive part 34 is formed byscreen printing, for example, a soldering paste on the through holelocated at the position where conduction is desired, and heat-treatingsame to fill the through hole with the soldering paste, and the metaljoined with the electrode of a semiconductor wafer. The aforementionedeach conductive part 34 has a bump 36 on the opposite end from the sidewhere the porous adhesive sheet 1 is adhered to a semiconductor wafer32. The bump 36 is, as shown in FIG. 4, formed in a ball shapeprotruding to form a convex on one side A1 of porous adhesive sheet 1 inthe thickness direction. Such bump 36 can be formed by controlling thethickness of conductive part 34 during the above-mentioned screenprinting, or by again applying screen printing and heat treatment.

The porous adhesive sheet 1 shown in FIG. 1 is free of the need for acontrol of the fluidity of the adhesive material, unlike theconventional underfill materials wherein the space between asemiconductor element and a substrate is filled with a liquid resin forbare chip mounting to adhere them, and therefore, can be used to form asemiconductor wafer with a porous adhesive sheet 31 shown in FIG. 4 bysimply adhering not only a semiconductor element but also asemiconductor wafer 32. By dividing such semiconductor wafer with aporous adhesive sheet 31 into small pieces, a semiconductor element witha small size porous adhesive sheet, which has a conductive part 34 onthe electrode 33, can be produced. This semiconductor element can besuitably adhered to a substrate and the like on the surface of the smallsize porous adhesive sheet, which is opposite from the adhesion surfaceto a semiconductor element (aforementioned surface 1 a of one side A1 inthe thickness direction in FIG. 4).

The above-mentioned semiconductor element with a small size porousadhesive sheet has a bump 36 at the tip of the conductive part 34. Thebump 36 is formed in a ball shape on the end of each conductive part 34that stands generally perpendicularly from the electrode 33 of thesemiconductor element in the thickness D1 of the porous adhesive sheet1. When the semiconductor element is adhered to a substrate, thesemiconductor element and the substrate do not need to be adhered in theentirety, unlike the case of conventional underfill materials. Due tothe presence of bump 36, the distance between the semiconductor elementand the substrate can be sufficiently ensured via the bump 36.Therefore, occurrence of defective connection due to the differentexpansion coefficients of the semiconductor element and the substratecan be prevented.

When only the through hole 2 located on the electrode 33 of thesemiconductor wafer 32, from among the through holes 2, is filled with aconductive material to form a conductive part 34, cavity through holes 2come to exist between the semiconductor element and the substrate. Thisenables adhesion of a semiconductor element having superior dielectricproperty to a substrate. When, after adhesion of a porous adhesive sheet1 to a semiconductor wafer 32, a through hole 2 not located on theelectrode 33 is filled with an adhesive material, a low elasticmaterial, a low linear expansive material and the like as necessary, asemiconductor wafer with a porous adhesive sheet, which showsadhesiveness, low elasticity, low linear expansion property and thelike, can be produced.

FIG. 5 shows a simplified sectional view of one preferable embodiment ofa semiconductor wafer with a porous adhesive sheet 41 of the presentinvention, which is on one virtual plane in parallel with theabove-mentioned thickness direction A and passing a through hole 12 andan electrode 33. A semiconductor wafer with a porous adhesive sheet 41is the same as the above-mentioned semiconductor wafer with a porousadhesive sheet 31 shown in FIG. 4 except that a porous adhesive sheet 11shown in FIG. 2 is used instead of the porous adhesive sheet 1, whereinthe parts having the same constitution as in FIG. 2 and FIG. 4 areindicated with like numbers and the explanation thereof is omitted.

In the semiconductor wafer with a porous adhesive sheet 41 shown in FIG.5, the porous adhesive sheet 11 has an organic material layer 14. As aresult, in addition to the above-mentioned respective effects of thesemiconductor wafer with a porous adhesive sheet 31 of FIG. 4, a greateropening area of each through hole 12 is retained in the porous adhesivesheet 11. Therefore, a high grade semiconductor wafer with a porousadhesive sheet 41 that easily affords thermal conductivity, control ofdielectric property and the like can be provided.

FIG. 6 shows a simplified sectional view of one preferable embodiment ofa semiconductor wafer with a porous adhesive sheet 51 of the presentinvention, which is on one virtual plane in parallel with theabove-mentioned thickness direction A and passing a through hole 22 andan electrode 33. A semiconductor wafer with a porous adhesive sheet 51is obtained by adhering a porous adhesive sheet 21 shown in FIG. 3 toone surface 32 a of a semiconductor wafer 32 and filling the throughhole 22 located on the electrode 33 with a conductive material to form aconductive part 34. The parts having the same constitution as in FIG. 3and FIG. 5 are indicated with like numbers and the explanation thereofis omitted.

The porous adhesive sheet 21 used for the semiconductor wafer with aporous adhesive sheet 51 shown in FIG. 6 has an organic material layer24 and an adhesive material layer 25 a, and is adhered to the side wherean adhesive material layer 25 a is formed, or adhered such that onesurface 21 a of one side A1 in the thickness direction comes intogeneral contact with the entirety of one surface 32 a of thesemiconductor wafer 32.

In the semiconductor wafer with a porous adhesive sheet 51 as shown inFIG. 6, the adhesive material layer 25 a is formed on a surface 21 a onthe side of the porous adhesive sheet 21 (the aforementioned one side A1in the thickness direction) to be adhered to a semiconductor wafer 32.As a result, in addition to the above-mentioned effects of asemiconductor wafer with a porous adhesive sheet 41 shown in FIG. 5, afirmer adhesion between the porous adhesive sheet 21 and thesemiconductor wafer 32 can be provided. Consequently, a semiconductorelement with a small size porous adhesive sheet obtained by dividing thesemiconductor wafer with a porous adhesive sheet 51 more stably securesadhesiveness between the small size porous adhesive sheet and asemiconductor element. Since the semiconductor element has a bump 36formed on the side opposite from the adhesion surface of the small sizeporous adhesive sheet to the semiconductor element (the aforementionedother side A2 in the thickness direction in FIG. 6), a strong adhesionto the circuit on the substrate is achieved, thereby decreasing theresistance value of the junction. With regard to the porous adhesivesheet having the above-mentioned adhesive material layer, when theadhesive material layer is made from a thermosetting oligomer, as inFIG. 6, the thermosetting oligomer becomes a thermoset resin having athree-dimensional structure, when it is adhered to a semiconductor waferto produce a semiconductor wafer with a porous adhesive sheet.

A semiconductor wafer with a porous adhesive sheet of the presentinvention, which is equipped with a porous adhesive sheet comprising anorganic material layer and an adhesive material layer, is not limited tothe embodiment of FIG. 6. However, it is preferable that the adhesivematerial layer be realized to form only one side of the porous adhesivesheet.

In the following, the production method of the porous adhesive sheet ofthe present invention is shown.

The production method of the porous adhesive sheet of the presentinvention basically comprises a step for forming a wire-containing filmfor forming an adhesive organic film, wherein plural wires aboutparallel with each other penetrate generally along the thicknessdirection, and a wire-removing step for removing the wires in theorganic film.

The step for forming a wire-containing film comprises, for example, thefollowing steps.

Wires made of a metal material are covered with a material forming anorganic film of the aforementioned porous adhesive sheet of the presentinvention. The metal materials preferable as the wire include copper,gold, aluminum and stainless steel. As the wire, a water-soluble fibersuch as polyvinyl alcohol and the like may be used. The wire used has anabout congruent sectional shape in each virtual plane perpendicular tothe central axis. The above-mentioned sectional shape of the wire is notparticularly limited and may be round, square, triangular or othershape, preferably round, more preferably circular, which is determinedas appropriate according to the object of the porous adhesive sheet ofthe present invention.

The above-mentioned coated wire is coil wound around the core member toform a roll-like wound coil. The coil winding is done according to aknown technique to produce an electromagnetic coil, such as relay,transformer and the like, and may be a spindle method wherein a coremember is rotated, a flyer method wherein a wire is wound, and the like.The coil winding includes, for example, a typical method wherein onewire is wound around a core member, a method wherein plural wires arewound around a core member and the like. When plural wires are woundaround a core member, the sectional shape in a virtual planeperpendicular to the central axis of each wire may be about congruent ordifferent from each other, but preferably, about congruent.

For coil winding, an irregular winding at a long feed pitch and a highspeed rotation, and a closest packing comprising solid coiling at arelatively slow speed and a feed pitch of about outer diameter of thewire, and dense stacking of the wires on the under layer wires, as inthe trefoil formation, are exemplified. These modes of coil winding canbe determined depending on wire diameter, cost, use and the like. Fromthe aspect of quality, a closest packed one is preferable. The coilwinding specification such as a winding width (total length of bobbinfor electromagnetic coil, relating to the number of turns in one layer),a thickness (relating to the number of layers) and the like can beappropriately determined depending on the size of the objective porousadhesive sheet.

A wound coil being formed by the aforementioned coil winding or acompleted wound coil after completion of the aforementioned coil windingis subjected to heating and/or pressurization. For the heating and/orpressurization, a process for applying only heating or simultaneouslyapplying heating and pressurization is preferable because a certaintension has been already applied during the coil winding. By thisprocess, the adjacent wires covered with a material for forming organicfilms are fused and/or pressed integrally to give a wound coil block.

The temperature for heating can be appropriately determined according tothe material for forming an organic film. Generally, it is aboutsoftening temperature of the material—300° C., specifically about 50°C.–300° C. When the organic film is produced from a thermosettingpolymer, heating at a temperature lower than the setting temperature ispreferable. When pressurized, the pressure is preferably about 0.098MPa–9.8 MPa, more preferably 0.196 MPa–1.96 MPa.

The aforementioned wound coil block is preferably formed such that therespective wires are insulated from each other. As a result, a porousadhesive sheet of the present invention can be preferably produced,wherein the wires in the wire-containing film mentioned below areinsulated from each other, and when the above-mentioned through holesare filled with conductive materials, the respective conductivematerials are insulated from each other.

Using a film-forming means, the aforementioned wound coil block issliced in thin sheets to give wire-containing films. The manner ofslicing can be freely determined depending on the mode of the objectiveporous adhesive sheet, and may be, for example, slicing without a coremember, slicing with a core member, slicing with a core member, followedby separation of the core member and the like. The block is sliced suchthat the plane that generally perpendicularly intersects with thecentral axis of the wound wire is the section, and the porous adhesivesheet has a thickness D1 meeting the object. The coil winding directionof the wound coil block corresponds to the penetrating direction of eachthrough hole, which is generally along the sheet thickness directionwhen it is formed into a porous adhesive sheet later.

The above-mentioned film-forming means includes any cutting means, suchas a cutting tool for slicing and the like, which can be determinedappropriately according to the object. For obtaining only onewire-containing film from one wound coil block, the above-mentionedfilm-forming means may be any of various means for cutting and grindingfrom the both sides of the wound coil block. Each surface of awire-containing film may be finished as necessary.

After a step for forming a wire-containing film for forming awire-containing film by the above-mentioned series of operations, awire-removing step for removing the wires in the organic film isapplied. To be specific, when a metal material is used as the wire, thewires in the wire-containing film are removed by acid or alkalineetching. When a water-soluble fiber is used as the wire, the wires inthe wire-containing film are removed by water washing. The space left bythe removal of the wires forms plural through holes running in aboutparallel with each other in the thickness direction of an organic film.

By these production methods, the porous adhesive sheet of the presentinvention is produced. For example, when a wire having any sectionalshape of about congruent circle is used, the above-mentioned porousadhesive sheet 1 of the present invention as shown in FIG. 1 can bepreferably produced. Different from conventional porous adhesive sheetshaving through holes formed by laser beam machining or photoprocessing,a porous adhesive sheet of the present invention having a through holeshowing a ratio Smin/Smax (%) of the minimum area (Smin) to the maximumarea (Smax) of the sections in the diameter direction of preferably85%–100%, more preferably 90%–100%, can be preferably produced by suchproduction method. In other words, by the above-mentioned productionmethod, a porous adhesive sheet of the present invention, wherein theopening ratio after formation of through holes in one surface of oneside in the thickness direction and that in one surface of the otherside in the thickness direction are almost identical, can be preferablyproduced.

Moreover, in the production method of the porous adhesive sheet of thepresent invention, the wire used for the above-mentioned productionmethod may be covered with an organic material having a softeningtemperature higher than that of the material forming the organic film bynot less than 10° C., preferably not less than 30° C. Speaking indetail, for the first operation in the above-mentioned step for forminga wire-containing film, a wire is covered with an organic materialhaving the above-mentioned softening temperature, and the organicmaterial is covered with the above-mentioned material forming theorganic film of the porous adhesive sheet of the present invention. By aseries of operations similar to the above-mentioned, a wire-containingfilm is formed and the wires are removed from the wire-containing film.As a result, the porous adhesive sheet of the present invention 11having the above-mentioned organic material layer 14 surrounding eachthrough hole 12 shown in FIG. 2 can be preferably produced.

The production method of the present invention may further comprise, ina stage before the above-mentioned wire-removing step, a wire protrusionstep for protruding, from the film surface, a wire end on at least onesurface side of a wire-containing film and an adhesive material formingstep for forming an adhesive material to fill the difference between theprotrusion of the wire resulting from the wire protrusion step and thefilm surface. The wire protrusion step may comprise removing a partforming the surface of the organic film appropriately by etching toprotrude the wire, or plating an end of the wire exposed on thewire-containing organic film to protrude the wire. In the subsequentadhesive material layer forming step, the difference between theaforementioned protrusion of the wire and the film surface is filledwith an adhesive material to form an adhesive material layer. Asmentioned above, the adhesive material layer is made from athermoplastic resin or thermosetting polymer having a softeningtemperature lower than that of the organic film by 10° C.–30° C., or athermosetting oligomer having a melt start temperature lower than thesoftening temperature of the organic film by at least 10° C., during thefilm forming. After the adhesive material layer forming step, the wiresare removed in the above-mentioned wire-removing step.

Here, the above-mentioned difference between the protrusion of the wireand the film surface is determined to have a length that does not blockthe through hole when the organic film of the produced porous adhesionfilm is adherable. This difference corresponds to the thickness D3 ofthe above-mentioned adhesive material layer. This difference isdetermined to be, for example, 1%–10%, preferably 5%–10%, of thediameter of the wire when the aforementioned sectional shape of eachwire is an about congruent circle. As a result, when the wire is formedby protrusion from only one surface of the organic film, theabove-mentioned porous adhesive sheet of the present invention 21 havingan adhesive material layer 25 a as shown in FIG. 3 can be preferablyproduced.

At this point, the porous adhesive sheets of the present invention 1,11, 21 shown in FIG. 1–FIG. 3 as preferable embodiments are preferablyproduced by the above-mentioned respective production methods. Themethods for producing the porous adhesive sheets 1, 11, 21 are notlimited by the above-mentioned production methods, but may be producedaccording to a production method other than those mentioned above.

A production method of a semiconductor wafer with a porous adhesivesheet of the present invention is shown in the following.

The production method of a semiconductor wafer with a porous adhesivesheet of the present invention comprises an adhesion step for adheringthe porous adhesive sheet of the present invention to one surface of asemiconductor wafer having one or plural electrodes on at least onesurface thereof, and a conductive part-forming step for filling at leastthe through holes located on an electrode of a semiconductor wafer, fromamong the plural through holes in a porous adhesive sheet, with aconductive material and connecting the electrode and the conductivematerial. The conductive part-forming step includes a step for forming abump on an end of a through hole filled with a conductive material,which is opposite from the side joined with the electrode, after fillingwith the above-mentioned conductive material. In this way, a conductivepart is formed.

A method for the above-mentioned adhesion step is not particularlylimited and may be a conventionally known method based on, for example,autoclave, heating with press and the like or pressurization. A methodfor the conductive part-forming step is not particularly limited and maybe a conventionally known method such as screen printing and the like.

When, for example, the porous adhesive sheet 1 shown in FIG. 1 is usedas the porous adhesive sheet of the present invention, a semiconductorwafer with a porous adhesive sheet 31 of FIG. 4 is preferably produced,when the porous adhesive sheet 11 shown in FIG. 2 is used, asemiconductor wafer with a porous adhesive sheet 41 of FIG. 5 ispreferably produced, and when the porous adhesive sheet 21 shown in FIG.3 is used, a semiconductor wafer with a porous adhesive sheet 51 of FIG.6 is preferably produced.

As a result, the semiconductor wafers having a porous adhesive sheet ofthe present invention 31, 41 or 51 shown in FIG. 4–FIG. 6 as preferableembodiments are preferably produced by the above-mentioned respectiveproduction methods. The methods for producing the semiconductor waferwith a porous adhesive sheet 31, 41 or 51 are not limited to theabove-mentioned production methods, but may be produced according to aproduction method other than those mentioned above.

EXAMPLES

The present invention is explained in detail in the following byreferring to Examples, which are mere examples and not to be construedas limitative.

Example 1

From a 100 μm-thick polycarbodiimide film (softening temperature: 150°C.) containing plural 30 μm diameter copper wires surrounded by a 5μm-thick polyamideimide resin (softening temperature: 170° C.), whichwas an organic material layer, were removed the wires by etching to givea porous adhesive sheet of the present invention. This porous adhesivesheet was adhered to a substrate at 160° C. As a result, the openingratio did not change before and after the adhesion and was 40%.

The opening ratio was calculated by a computer after importing images bya microscope with a CCD camera. The softening temperature was determinedfrom the temperature of inflection point when measured by raising thetemperature at 10° C./min on a tension mode of TMA (thermomechanicalanalysis). The results are shown in Table 1.

Example 2

From a 50 μm-thick polycarbodiimide film (softening temperature: 150°C.) containing plural 18 μm diameter copper wires surrounded by a 2μm-thick polyamideimide resin (softening temperature: 170° C.), whichwas an organic material layer, were removed the wires by etching to givea porous adhesive sheet of the present invention. This porous adhesivesheet was adhered to a substrate at 160° C. As a result, the openingratio did not change before and after the adhesion and was 60%. Theresults are shown in Table 1.

TABLE 1 Example 1 Example 2 Film forming material PolycarbodiimidePolycarbodiimide resin resin Softening temperature 150° C. 150° C. Filmthickness 100 μm 50 μm Diameter of through  30 μm 18 μm hole Organicmaterial Polyamideimide Polyamideimide resin resin Softening temperature170° C. 170° C. Thickness of organic  5 μm  2 μm material layer Openingratio after 40% 60% adhesion

Example 3

From a 150 μm-thick polycarbodiimide film (softening temperature: 150°C.) having adhesiveness and insulating property and containing plural 80μm diameter copper wires surrounded by a 5 μm-thick polyamideimide resin(softening temperature: 170° C.), which was an organic material layer,were removed the wires by etching to give a porous adhesive sheet of thepresent invention. This porous adhesive sheet was adhered to asemiconductor wafer at 190° C. and 1.96 MPa (20 kgf/cm²) in anautoclave. As a result, the opening ratio was 60%.

A solder was used to fill only the through hole located on an electrodeof the semiconductor wafer with a porous adhesive sheet by screenprinting to give a conductive part having a bump. The semiconductorwafer with a porous adhesive sheet of the present invention thusprepared was diced into 8 mm square chips, and connected to thesubstrate. As a result, the rate of electrical connection was 100%. Theresults are shown in Table 2.

TABLE 2 Example 3 Film forming material Polycarbodiimide resin Softeningtemperature 150° C. Film thickness 150 μm Diameter of through hole  80μm Organic material Polyamideimide resin Softening temperature 170° C.Thickness of organic material  5 μm layer Opening ratio after adhesion 60% Rate of electrical connection 100%

Example 4

From a 70 μm-thick polycarbodiimide film (softening temperature: 150°C.) having adhesiveness and insulating property and containing plural 50μm diameter copper wires surrounded by a 3 μm-thick polyamideimide resin(softening temperature: 170° C.), which was an organic material layer,was removed by plasma etching the organic film surface (5 μm) except thewires and the organic material layer to protrude the wires. Thereto wasapplied an unreacted liquid thermosetting resin composition comprising abisphenol A type epoxy resin (Ep827) and methylhexahydrophthalicanhydride (NH-8210) in admixture at a weight ratio of 1:1, followed byheating at 100° C. for 30 min to give a 5 μm-thick adhesive materiallayer made from a thermosetting oligomer (melt start temperature: 120°C.). The wires were removed by alkali etching to give the porousadhesive sheet of the present invention. The prepared adhesive sheet hadan opening ratio of 40%. This porous adhesive sheet was adhered to asemiconductor wafer at 120° C. and 1.96 MPa (20 kgf/cm²) in anautoclave.

A solder was used to fill only the through hole located on an electrodeof the semiconductor wafer with a porous adhesive sheet by screenprinting to give a conductive part having a bump. The semiconductorwafer with a porous adhesive sheet of the present invention thusprepared was diced into 8 mm square chips, and adhered to the substrate.As a result, the rate of electrical connection was 100%.

The opening ratio after adhesion was 40%, and did not change before andafter the adhesion. The results are shown in Table 3.

TABLE 3 Example 4 Film forming material Polycarbodiimide resin Softeningtemperature 150° C. Film thickness 70 μm Diameter of through hole 50 μmOrganic material Polyamideimide resin Softening temperature 170° C.Thickness of organic material  3 μm layer Adhesive material Epoxy resinoligomer Melt start temperature 120° C. Thickness of adhesive material 5 μm layer Opening ratio after adhesion  40% Rate of electricalconnection 100%

Comparative Example

A porous adhesive sheet obtained by laser beam machining a 100 μm-thickpolyimide film to have through holes having a diameter on the filmsurface side of 120 μm, on the back of the film of 60 μm and an averageof 90 μm was adhered to a semiconductor wafer in an autoclave. Afteradhesion, a conductive part having a bump was formed by screen printingon the film surface side in the same manner as in Example 4.

By an appearance examination, some connected bumps were observed.

Effect of the Invention

As is clear from the above explanation, the present invention provides aporous adhesive sheet having a number of fine through holes, each havinga regular shape and being difficult to close when an organic film isadherable, and a preferable production method thereof, and asemiconductor wafer with a porous adhesive sheet, which is suitable forbare chip mounting and a production method thereof.

This application is based on application Nos. 2000-005084 and2000-243398 filed in Japan, the contents of which are incorporatedhereinto by reference.

1. A production method of a porous adhesive sheet having plural throughholes running in about parallel with each other in the thicknessdirection of an adhesive organic film, which are surrounded by anorganic material layer having a softening temperature higher by 10° C.or more than the softening temperature of the organic film, which methodcomprises a step for forming a wire-containing film, comprising coveringthe wire with an organic material having a softening temperature higherby 10° C. or more than the softening temperature of the adhesive organicfilm and forming a wire-containing film, such that plural wires run inabout parallel with each other in the thickness direction of theadhesive organic film, and a wire-removing step for removing the wire inthe organic film.
 2. The production method of claim 1, furthercomprising, between the aforementioned step for forming awire-containing film and the wire-removing step, a wire protrusion stepfor protruding a wire end on at least one surface side of thewire-containing film from the film surface, and an adhesive materiallayer-forming step for forming an adhesive material layer composed of athermoplastic resin or thermosetting-polymer having a softeningtemperature lower than that of the organic film by 10° C.–30° C., whichfills a difference between the aforementioned wire protrusion and thefilm surface.
 3. The production method of claim 1, further comprising,between the aforementioned step for forming a wire-containing film andthe wire-removing step, a wire protrusion step for protruding a wire endon at least one surface side of the wire-containing film from the filmsurface, and a step for forming an adhesive material layer composed of athermosetting oligomer having a melt start temperature lower than thesoftening temperature of the organic film by not less than 10° C.,which-fills a difference between the aforementioned wire protrusion andthe film surface.
 4. The production method of claim 1, wherein the wiresare insulated from each other.
 5. The production method of claim 2wherein the wires are insulated from each other.
 6. The productionmethod of claim 3 wherein the wires are insulated from each other.